There seems to be a problem with adding health to weapons via the forging/weaponry skill.
From what I have observed and tested, I would STRONGLY advise you not try to add health to your weapons for you will surely regret it.
Forging armour seems totally unaffected so knock yourself out.
Proteus, god of the sea
Written by my hand on the 12th of Midwinter, in the year 1055.